The present invention relates to an improvement in a reel-to-reel tape cassette.
As shown in FIG. 1 of the accompanying drawings, a conventional tape cassette includes a cassette half 1 lined interiorly with a film or sheet 2 of tetrafluoroethylene or Teflon.TM. to facilitate transport of a tape 3. Direct frictional contact between the tape 3 and the sheet 2, however, causes a frictional sound. Such direct frictional contact is also disadvantageous in that as the diameter of the tape roll varies, the area of contact between the tape roll wound on the reel hub and the sheet also varies, resulting in a fluctuation of the back tension to which the tape is subjected. Another problem with the prior tape cassette is that the characteristics of the sheet vary with temperature and humidity, causing back tension fluctuations responsible for irregular tape winding and tape elongation.
To eliminate the foregoing difficulties, there has been proposed a tape cassette including reel hubs (hereinafter referred to as a "reel") disposed in a cassette half and having flanges made of a relatively rigid and heavy material.
These reels are highly advantageous when used on open-reel tape decks. However, they cause reel-to-reel tape cassettes to suffer from the following shortcomings.
Due to the large inertia of the reel upon rotation, the reel fails to stop quickly. This causes an increased length of tape to tend to be forced off or loosened from the reel. When the tape is to be driven again, no back tension is imposed on the tape, a condition which prevents optimum recording and playback operation. Furthermore, the tape is likely to be displaced onto the upper surface of the flanges and the lower surface of the cassette, with the result that the tape cannot travel or is cut.
Tapes for use on open reels have a relatively large thickness of from 29 to 53.mu., and hence are less subject to damage even when brought into contact with the reel flange. However, tapes for use in tape cassettes are relatively thin, say 9 to 18.mu., and more prone to damage when in contact with the reel flange. This difficulty becomes fatal especially when the tape is to be wound or rewound at high speed.
The reel flange produces noise when it hits the cassette half during rotation of the flange, and the noise thus generated is irritating particularly when the tape deck is in a fast forward or rewinding mode of operation.
If the reel remains unlocked and freely rotatable when the cassette is carried about, the tape tends to be unwound from the reel due to vibration, and the unreeled tape may become entangled with the reel or subjected to no back tension.